1. Field of the Invention
The present invention relates to valves and, in particular, to a valve which opens or closes after a fluid proximate the valve has undergone a predetermined number of pressure cycles.
2. Description of the Prior Art
Often, medical equipment and instruments are sterilized within a chamber, referred to as a sterilizer, which contains a fluid that undergoes periodic variations in pressure as the articles are sterilized. Also, it is common for sterilized articles to be stored for a period of time after they are sterilized and before they are used. Of course, the sterilized articles must remain sterile during that time period.
Accordingly, workers in the art have developed a container for holding articles as they are sterilized. The container permits exposure of the articles to the fluid within the sterilizer during a part of the time the container is within the sterilizer. The container is sealed automatically upon completion of the sterilization cycle. Known containers generally employ a valve which is open when the pressure exerted by the fluid within the sterilizer is above a predetermined high value and is closed when the pressure is below a predetermined low value. Commonly, the sterilizer is under a high pressure condition when a sterilizing medium is present within the sterilizer. Therefore, the valve is open whenever the sterilizing medium is within the sterilizer to permit exposure of the articles within the container to the sterilizing medium, and is closed at all other times. When the sterilization cycle is completed, the pressure within the sterilizer is at the predetermined low value and the valve closes to seal the container and preserve the sterility of the articles after the container is removed from the sterilizer.
However, maximum sterilization and drying of the articles can be achieved only if the container is exposed to the interior of the sterilizer during the entire course of the sterilization cycle. With the use of the containers of the type described above, the articles within the container are exposed to the interior of the sterilizer only during a part of the sterilization cycle.
Therefore, there exists a need for a valve for a sterilizer container that permits exposure of the articles within the container to the entire sterilization cycle and seals the articles within the container upon completion of the sterilization cycle.